BR112019026971B1 - HIGH BANDWIDTH RESIDUAL PREDICTION WITH INTER-CHANNEL BANDWIDTH EXTENSION IN THE TIME DOMAIN - Google Patents

Abstract

One method includes decoding a lowband portion of an encoded Mid signal to generate a lowband decoded Mid signal. The method further includes processing the decoded lowband Mid signal to generate a lowband residual prediction signal and generating a lowband left channel and a lowband right channel based partially on the decoded lowband Mid signal and the lowband signal. low-band residual prediction. The method further includes decoding a highband portion of the encoded Mid signal to generate a time domain decoded highband Mid signal and processing the time domain decoded highband Mid signal to generate a highband residual prediction signal. in the time domain. The method also includes generating a high-band left channel and a high-band right channel based on the time-domain decoded high-band Mid signal and the time-domain high-band residual prediction signal.

Description

I. Priority Claim

[0001] This application claims priority benefit from Commonly Owned US Provisional Patent Application No. 62/526,854, filed on June 29, 2017, and US Non-Provisional Patent Application No. 16/ 000.551, filed June 5, 2018, the contents of each of the aforementioned applications being expressly incorporated herein by reference in their entirety.

II. Field

[0002] The present description is in general terms related to the coding of multiple audio signals.

III. Description of the Related Technique

[0003] Advances in technology have resulted in smaller and more powerful computing devices. For example, a variety of portable personal computing devices, including cordless phones such as cell phones and smart phones, tablets and laptops, are small, lightweight and easy for users to carry. These devices can communicate voice and data packets over wireless networks. In addition, many of these devices incorporate additional functionality, such as a digital still camera, a digital video camera, a digital recorder and an audio file player. In addition, these devices can process executable instructions, including software applications, such as a web browser, that can be used to access the Internet. As such, these devices can include significant computational resources.

[0004] A computing device may include or may be coupled to multiple microphones to receive audio signals. Generally, a sound source is closer to a first microphone than a second microphone of the multiple microphones. Therefore, a second audio signal received from the second microphone may be delayed with respect to a first audio signal received from the first microphone due to the microphones' respective distances from the sound source. In other implementations, the first audio signal may be delayed relative to the second audio signal. In stereo encoding, audio signals from microphones can be encoded to generate a mid signal and one or more side signals. The mid signal corresponds to a sum of the first audio signal and the second audio signal. A side signal corresponds to a difference between the first audio signal and the second audio signal.

IV. summary

[0005] In a particular implementation, a device includes a lowband mid signal decoder configured to decode a lowband portion of an encoded mid signal to generate a decoded lowband mid signal. The device also includes a lowband residual prediction unit configured to process the decoded lowband mid signal to generate a lowband residual prediction signal. The device further includes an up-mix processor configured to generate a lowband left channel and a lowband right channel based partially on the decoded lowband mid signal and the lowband residual prediction signal. The device also includes a high band mid signal decoder configured to decode a high band portion of the encoded mid signal to generate a time domain decoded high band mid signal. The device further includes a high-band residual prediction unit configured to process the time-domain decoded high-band mid signal to generate a high-band time-domain residual prediction signal. The device also includes an inter-channel bandwidth extension decoder configured to generate a high-band left channel and a high-band right channel based on the time-domain decoded high-band mid signal and the residual prediction signal. high bandwidth in the time domain.

[0006] In another particular implementation, a method includes decoding a lowband portion of an encoded mid signal to generate a decoded lowband mid signal. The method also includes processing the decoded lowband mid signal to generate a lowband residual prediction signal and generating a lowband left channel and a lowband right channel based partially on the decoded lowband mid signal and the lowband mid signal. low-band residual prediction. The method further includes decoding a highband portion of the encoded mid signal to generate a decoded highband mid signal and processing the decoded highband mid signal to generate a highband residual prediction signal. The method further includes generating a highband left channel and a highband right channel based on the decoded highband mid signal and the highband residual prediction signal.

[0007] In another particular implementation, a non-transient computer-readable medium includes instructions that, when executed by a processor within a decoder, cause the decoder to perform operations including decoding a low-band portion of a mid signal encoded to generate a decoded low-band mid signal. Operations also include processing the decoded lowband mid signal to generate a lowband residual prediction signal and generating a lowband left channel and a lowband right channel based partially on the decoded lowband mid signal. and the low-band residual prediction signal. The operations also include decoding a highband portion of the encoded mid signal to generate a decoded highband mid signal and processing the decoded highband mid signal to generate a highband residual prediction signal. The operations also include generating a highband left channel and a highband right channel based on the decoded highband mid signal and the highband residual prediction signal.

[0008] In another particular implementation, an apparatus includes means for decoding a lowband portion of an encoded mid signal to generate a decoded lowband mid signal. The device also includes means for processing the decoded lowband mid signal to generate a lowband residual prediction signal and means for generating a lowband left channel and a lowband right channel based partially on the decoded lowband mid signal. and the low-band residual prediction signal. The device further includes means for decoding a highband portion of the encoded mid signal to generate a decoded highband mid signal and means for processing the decoded highband mid signal to generate a highband residual prediction signal. The device also includes means for generating a highband left channel and a highband right channel based on the decoded highband mid signal and the highband residual prediction signal.

[0009] Other implementations, advantages, and features of the present description will become apparent upon review of the entire application, including the following sections: Brief Description of Drawings, Detailed Description, and Claims.

V. Brief Description of the Drawings

[0010] FIG. 1 is a block diagram of a particular illustrative example of a system including a decoder operable to predict a high-band residual channel and to perform time-domain inter-channel bandwidth extension (ICBWE) decoding operations;

[0011] FIG. 2 is a diagram illustrating the decoder of FIG. 1;

[0012] FIG. 3 is a diagram illustrating an ICBWE decoder;

[0013] FIG. 4 is a particular example of a method for predicting a high-band residual channel;

[0014] FIG. 5 is a block diagram of a particular illustrative example of a mobile device that is operable to predict a high-band residual channel and to perform time-domain ICBWE decoding operations; It is

[0015] FIG. 6 is a block diagram of a base station that is operable to predict a high-band residual channel and to perform time-domain ICBWE decoding operations.

SAW. Detailed Description

[0016] Particular aspects of the present description are described below with reference to the drawings. In the description, common features are designated by common reference numbers. As used in this document, various terminologies are used for the purpose of describing particular implementations only and are not intended to limit implementations. For example, the singular forms "a", "an", "the" and "a" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It can be further understood that the terms "comprises" and "comprising" may be used interchangeably with "includes" or "including". Additionally, it will be understood that the term "where" may be used interchangeably with "where". As used in this document, an ordinal term (for example, "first", "second", "third", etc.) used to modify an element, such as a structure, a component, an operation etc., is not in itself indicative of any priority or order of the element relative to another element, but only distinguishes the element from another element of the same name (but to use the term ordinal). As used herein, the term "set" refers to one or more of a particular element, and the term "plurality" refers to multiples (e.g., two or more) of a particular element.

[0017] In the present description, terms such as "determination", "calculation", "change", "adjustment" etc. can be used to describe how one or more operations are performed. It should be noted that these terms are not to be construed as limiting and other techniques may be used to perform similar operations. Additionally, as referred to in this document, "generate", "calculate", "use", "select", "access" and "determine" may be used interchangeably. For example, "generate", "calculate" or "determine" a parameter (or a signal) can refer to actively generating, calculating or determining the parameter (or signal) or it can refer to using, selecting or accessing the parameter ( or signal) already generated, such as by another component or device.

[0018] Operable systems and devices for encoding and decoding multiple audio signals are described. A device may include an encoder configured to encode multiple audio signals. Multiple audio signals can be captured simultaneously in time using multiple recording devices, for example multiple microphones. In some instances, multiple audio signals (or multichannel audio) can be synthetically (eg, artificially) generated by multiplexing multiple audio channels that are recorded at the same time or at different times. As illustrative examples, simultaneous recording or multiplexing of audio channels can result in a 2-channel configuration (i.e. Stereo: Left and Right), a 5.1-channel configuration (Left, Right, Center, Left Surround, Left Surround, Right and Low Frequency Emphasis (LFE)), a 7.1-channel configuration, a 7.1 + 4-channel configuration, a 22.2-channel configuration, or an N-channel configuration.

[0019] Audio capture devices in teleconference rooms (or telepresence rooms) may include multiple microphones that acquire spatial audio. Spatial audio can include speech as well as background audio that is encoded and streamed. Speech/audio from a given source (e.g., a speaker) may arrive at multiple microphones at different times, depending on how the microphones are arranged, as well as where the source (e.g., speaker) is located in relation to microphones and room dimensions. For example, a sound source (eg a speaker) may be closer to a first microphone associated with the device than a second microphone associated with the device. Thus, a sound emitted from the sound source can reach the first microphone before the second microphone. The device can receive a first audio signal through the first microphone and can receive a second audio signal through the second microphone.

[0020] Mid-side encoding (MS) and parametric stereo encoding (PS) are stereo encoding techniques that can provide greater efficiency over dual-mono encoding techniques. In dual-mono coding, the left (L) channel (or signal) and the right (R) channel (or signal) are coded independently, without making use of inter-channel correlation. MS encoding reduces the redundancy between a pair of correlated L/R channels by transforming the left and right channels into a sum channel and a difference channel (eg a side signal) before encoding. The sum signal (also referred to as the mid signal) and the difference signal (also referred to as the side signal) are encoded or encoded waveform based on an MS coding model. Relatively more bits are spent on the mid signal than on the side signal. PS encoding reduces redundancy in each subband by transforming the L/R signals into a sum signal (or mid signal) and a set of side parameters. The side parameters can indicate an inter-channel intensity difference (IID), an inter-channel phase difference (IPD), an inter-channel time difference (ITD), side or residual prediction gains, etc. The sum signal is waveform encoded and transmitted along with the side parameters. In a hybrid system, the side signal can be waveform encoded in the lower bands (e.g. less than 2 kilohertz (kHz)) and PS encoded in the higher bands (e.g. greater than or equal to 2 kHz) where the inter-channel phase preservation is perceptually less critical. In some implementations, PS encoding may be used in the lower bands as well to reduce inter-channel redundancy prior to waveform encoding.

[0021] MS encoding and PS encoding can be done in frequency domain or subband domain. In some examples, the Left channel and the Right channel may not be correlated. For example, the Left channel and the Right channel can include uncorrelated synthetic signals. When Left channel and Right channel are not correlated, the coding efficiency of MS encoding, PS encoding, or both can approach the coding efficiency of dual-mono encoding.

[0022] Depending on the recording setup, there may be a temporal shift between a Left and Right channel, as well as other spatial effects such as ambient echo and reverb. If the temporal offset and phase mismatch between the channels are not compensated for, the sum channel and the difference channel can contain comparable energies, reducing the coding gains associated with MS or PS techniques. The reduction in coding gains can be based on the amount of time (or phase) shift. The comparable sum signal and difference signal energies may limit the use of MS coding in certain frames where the channels are time shifted but highly correlated. In stereo encoding, a Mid signal (eg a sum channel) and a Side signal (eg a difference channel) can be generated based on the following formula: M=(L+R)/2, S= (L-R)/2, Formula 1

[0023] Where M corresponds to the Mid signal, S corresponds to the Side signal, L corresponds to the Left channel and R corresponds to the Right channel.

[0024] In some cases, the Mid signal and the Side signal can be generated based on the following formula: M=c(L+R), S = c(L-R), Formula 2

[0025] Where c corresponds to a complex value that is frequency dependent. The generation of the Mid signal and the Side signal based on Formula 1 or Formula 2 can be called "downmixing". A reverse process of generating the Left channel and the Right channel from the Mid signal and the Side signal based on Formula 1 or Formula 2 can be referred to as "upmixing".

[0026] In some cases, the Mid signal may be based on other formulas, such as: M=(L+gDR)/2 or Formula 3 M = g1L + g2R Formula 4

[0027] Where g1 + g2 = 1.0 and where gD is a gain parameter. In other examples, downmixing can be performed in bands, where mid(b) = c1L(b) + c2R(b), where c1 and c2 are complex numbers, where side(b) = c3L(b) - c4R(b) ) and where c3 and c4 are complex numbers.

[0028] An ad-hoc approach used to choose between MS encoding or dual-mono encoding for a particular frame may include generating a mid signal and a side signal, calculating the energies of the mid signal and the side signal, and determining whether the MS encoding must be performed based on the energies. For example, MS encoding can be performed in response to a determination that the ratio of energies of the side signal and the mid signal is less than a threshold. To illustrate, if a Right channel is shifted for at least the first time (for example, about 0.001 seconds or 48 samples at 48 kHz), a first energy of the mid signal (corresponding to the sum of the left signal and the right signal) can be comparable to a second side signal energy (corresponding to a difference between the left signal and the right signal) for voiced speech frames. When the first energy is comparable to the second energy, a larger number of bits can be used to encode the side signal, thus reducing the coding efficiency of MS encoding compared to dual-mono encoding. Dual-mono encoding can therefore be used when the first energy is comparable to the second energy (for example, when the ratio of the first energy and the second energy is greater than or equal to the threshold). In an alternative approach, the decision between MS encoding and dual-mono encoding for a particular frame can be made based on comparing a threshold and normalized cross-correlation values of the Left channel and the Right channel.

[0029] In some examples, the encoder may determine a mismatch value indicative of an amount of temporal misalignment between the first audio signal and the second audio signal. As used in this document, a "time skew value", a "skew value", and a "mismatch value" may be used interchangeably. For example, the encoder may determine a time offset value indicative of a shift (e.g. time mismatch) of the first audio signal relative to the second audio signal. The time mismatch value can correspond to an amount of time delay between receiving the first audio signal at the first microphone and receiving the second audio signal at the second microphone. In addition, the encoder can determine the time mismatch value on a frame-by-frame basis, for example, based on each 20 millisecond (msec) speech/audio frame. For example, the time mismatch value can correspond to an amount of time that a second frame of the second audio signal is delayed relative to a first frame of the first audio signal. Alternatively, the time mismatch value may correspond to an amount of time that the first frame of the first audio signal is delayed with respect to the second frame of the second audio signal.

[0030] When the sound source is closer to the first microphone than the second microphone, the frames of the second audio signal may be delayed with respect to the frames of the first audio signal. In that case, the first audio signal can be referred to as "reference audio signal" or "reference channel" and the second delayed audio signal can be referred to as "target audio signal" or "target channel". Alternatively, when the sound source is closer to the second microphone than the first microphone, the frames of the first audio signal may be delayed relative to the frames of the second audio signal. In that case, the second audio signal may be referred to as the reference audio signal or reference channel and the first delayed audio signal may be referred to as the target audio signal or target channel.

[0031] Depending on where the sound sources (eg announcers) are located in a conference or telepresence room or how the position of the sound source (eg announcer) changes in relation to the microphones, the reference channel and target channel can change from one frame to another; similarly, the time delay value can also change from one frame to another. However, in some implementations, the time mismatch value can always be positive to indicate an amount of delay of the "target" channel relative to the "reference" channel. Furthermore, the time mismatch value may correspond to a "non-causal deviation" value by which the delayed target channel is "pulled" in time such that the target channel is aligned (e.g., maximally aligned) with the "reference" channel. The downmix algorithm for determining the mid signal and the side signal can be performed on the reference channel and the non-causal bypassed target channel.

[0032] The encoder can determine the time mismatch value based on the reference audio channel and a plurality of time mismatch values applied to the target audio channel. For example, a first frame from the reference audio channel, X, can be received at a first time (m1). A particular first frame of the target audio channel, Y, can be received at a second time (n1) corresponding to a first time mismatch value, eg shift1 = n1 - m1. Furthermore, a second frame from the reference audio channel can be received at a third time (m2). A second particular frame from the target audio channel can be received at a fourth time (n2) corresponding to a second time mismatch value, eg shift2 = n2 - m2.

[0033] The device may perform a framing or buffering algorithm to generate a frame (e.g. 20 ms samples) at a first sample rate (e.g. 32 kHz sample rate (i.e. , 640 samples per frame)). The encoder may, in response to determining that a first frame of the first audio signal and a second frame of the second audio signal arrive at the device at the same time, estimate a time mismatch value (e.g., shiftl) as equal to zero samples. A Left channel (eg corresponding to the first audio signal) and a Right channel (eg corresponding to the second audio signal) can be time-aligned. In some cases, the Left channel and the Right channel, even when aligned, may differ in energy due to various reasons (eg microphone calibration).

[0034] In some examples, the Left channel and the Right channel may be temporarily misaligned due to various reasons (for example, a sound source, such as a speaker, may be closer to one of the microphones than the other and the two microphones can be greater than a limit (eg 1 - 20 centimeters) apart). A location of the sound source relative to the microphones can introduce different delays in the Left and Right channels. Also, there may be a gain difference, a power difference or a level difference between the Left channel and the Right channel.

[0035] In some examples, where there are more than two channels, a reference channel is initially selected based on the levels or energies of the channels and later refined based on the time mismatch values between different pairs of channels, for example, t1( ref, ch2), t2(ref, ch3), t3(ref, ch4), ... t3(ref, chN), where ch1 is the ref channel initially and t1(.), t2(.), etc. are the functions for estimating the mismatch values. If all time mismatch values are positive, then ch1 is treated as the reference channel. If any of the mismatch values are a negative value, then the reference channel will be reset to the channel that was associated with a mismatch value that resulted in a negative value, and the above process will continue until the best selection (e.g. with based on the maximum number of maximally decorrelated side signals) of the reference channel is reached. A hysteresis can be used to overcome any sudden variations in the reference channel selection.

[0036] In some instances, the arrival time of audio signals to microphones from multiple sound sources (eg, speakers) may vary when multiple speakers are speaking alternately (eg, without overlapping). In this case, the encoder can dynamically adjust a speaker-based time mismatch value to identify the reference channel. In some other examples, multiple speakers may be speaking at the same time, which may result in varying amounts of time mismatch, depending on which speaker is speaking loudest, closest to the microphone, etc. In this case, the identification of the reference and target channels can be based on the variable values of temporal deviation in the current frame and the estimated values of temporal mismatch in the previous frames, and based on the energy or the temporal evolution of the first audio signal and the second audio signal.

[0037] In some examples, the first audio signal and the second audio signal may be synthesized or artificially generated when the two signals potentially show less (eg, no) correlation. It should be understood that the examples described in this document are illustrative and may be instructive in determining a relationship between the first audio signal and the second audio signal in similar or different situations.

[0038] The encoder can generate comparison values (e.g., difference values or cross-correlation values) based on comparing a first frame of the first audio signal and a plurality of frames of the second audio signal. Each frame of the plurality of frames may correspond to a particular time mismatch value. The encoder can generate a first estimated time mismatch value based on the comparison values. For example, the first estimated time mismatch value may correspond to a comparison value indicating a higher temporal similarity (or lesser difference) between the first frame of the first audio signal and the first frame of the corresponding second audio signal.

[0039] The encoder can determine a final time mismatch value by refining, in several stages, a series of estimated time mismatch values. For example, the encoder may first estimate a "trial" time mismatch value based on the comparison values generated from preprocessed and resampled stereophonic versions of the first audio signal and the second audio signal. The encoder can generate interpolated comparison values associated with time mismatch values close to the estimated "attempt" time mismatch value. The encoder may determine a second "interpolated" estimated time mismatch value based on the interpolated comparison values. For example, the second "interpolated" estimated time mismatch value may correspond to a particular interpolated comparison value that indicates a higher temporal similarity (or lower difference) than the remaining interpolated comparison values and the first estimated time mismatch value of "attempt". If the second "interpolated" estimated time mismatch value of the current frame (for example, the first frame of the first audio signal) differs from the final time mismatch value of a previous frame (for example, a frame of the first audio signal preceding the first frame), then the "interpolated" time mismatch value of the current frame is "shifted" to improve the temporal similarity between the first audio signal and the second skewed audio signal. In particular, a third "shifted" estimated time mismatch value can correspond to a more accurate measure of temporal similarity by searching around the second "interpolated" estimated time mismatch value of the current frame and the final estimated time mismatch value of the frame. previous. The third "changed" estimated time mismatch value is further conditioned to estimate the final time mismatch value by limiting any spurious changes in the time mismatch value between frames and further controlled not to go from a negative time mismatch value to a value of positive time mismatch (or vice versa) in two successive (or consecutive) frames as described in this document.

[0040] In some examples, the encoder may refrain from switching between a positive time mismatch value and a negative time mismatch value or vice versa in consecutive frames or in adjacent frames. For example, the encoder can set the final time mismatch value to a particular value (e.g., 0) indicating that there is no time mismatch based on the estimated "interpolated" or "shifted" time mismatch value of the first frame and a corresponding estimated "interpolated" or "shifted" or final time mismatch value at a particular frame preceding the first frame. To illustrate, the encoder can set the final time-mismatch value of the current frame (for example, the first frame) to indicate no time-shift, that is, shift1 = 0, in response to determining that one of the estimated time-mismatch values "attempted" or "interpolated" or "changed" temporal mismatch of the current frame is positive and the other one of the estimated time mismatch values of "attempted" or "interpolated" or "changed" or "final" from the previous frame (e.g. , the frame preceding the first frame) is negative. Alternatively, the encoder can also set the final time mismatch value of the current frame (e.g., the first frame) to indicate no time shift, i.e., shift1 = 0, in response to determining that one of the current frame's estimated time mismatch values of "attempted" or "interpolated" or "changed" is negative and the other of the estimated time mismatch values of "attempted" or "interpolated" or " changed" or "end" of the previous frame (for example, the frame before the first frame) is positive.

[0041] The encoder can select a frame of the first audio signal or the second audio signal as a "reference" or a "target" based on the time mismatch value. For example, in response to determining that the final time mismatch value is positive, the encoder can generate a reference channel or signal indicator having a first value (e.g., 0) indicating that the first audio signal is a signal. "reference" and that the second audio signal is the "target" signal. Alternatively, in response to determining that the final time mismatch value is negative, the encoder may generate the reference channel or signal indicator having a second value (e.g., 1) indicating that the second audio signal is the signal "reference" and that the first audio signal is the "target" signal.

[0042] The encoder can estimate a relative gain (eg, a relative gain parameter) associated with the reference signal and with the noncausal deviated target signal. For example, in response to determining that the final time mismatch value is positive, the encoder can estimate a gain value to normalize or equalize the power or amplitude levels of the first audio signal relative to the second audio signal that is shifted by the noncausal time mismatch value (for example, an absolute value of the final time mismatch value). Alternatively, in response to the determination that the final time mismatch value is negative, the encoder may estimate a gain value to normalize or equalize the power or amplitude levels of the non-causally shifted first audio signal relative to the second audio signal. . In some examples, the encoder may estimate a gain value to normalize or equalize the amplitude or power levels of the "reference" signal relative to the non-causally deviated "target" signal. In other examples, the encoder can estimate the gain value (eg, a relative gain value) based on the reference signal relative to the target signal (eg, the unshifted target signal).

[0043] The encoder can generate at least one encoded signal (for example, a mid signal, a side signal, or both) based on the reference signal, the target signal, the non-causal time mismatch value, and the relative gain parameter . In other implementations, the encoder may generate at least one encoded signal (for example, a mid signal, a side signal, or both) based on the reference channel and the time mismatch adjusted target channel. The side signal can correspond to a difference between the first samples of the first frame of the first audio signal and the selected samples of a selected frame of the second audio signal. The encoder can select the selected frame based on the final time mismatch value. Fewer bits can be used to encode the side signal due to the reduced difference between the first samples and the selected samples compared to other samples of the second audio signal that correspond to a frame of the second audio signal that is received by the device at the same time than the first frame. A device transmitter may transmit at least one coded signal, the noncausal time mismatch value, the relative gain parameter, the reference channel or signal indicator, or a combination thereof.

[0044] The encoder can generate at least one encoded signal (for example, a mid signal, a side signal, or both) based on the reference signal, the target signal, the non-causal time mismatch value, the relative gain parameter , the lowband parameters of a particular frame of the first audio signal, the highband parameters of the particular frame, or a combination thereof. The private frame can precede the first frame. Certain lowband parameters, highband parameters, or a combination thereof, from one or more previous frames can be used to encode a mid signal, a side signal, or both, from the first frame. Coding the mid signal, the side signal, or both, based on the lowband parameters, the highband parameters, or a combination thereof, can improve estimates of the noncausal time mismatch value and the relative gain parameter inter-channel. Low band parameters, high band parameters or a combination thereof can include a pitch parameter, a loudness parameter, an encoder type parameter, a low band energy parameter, a high band energy parameter, an envelope parameter (for example, a tilt parameter), a pitch gain parameter, an FCB gain parameter, an encoding mode parameter, a voice activity parameter, a noise estimation parameter , a signal-to-noise ratio parameter, a formants parameter, a speech/music decision parameter, the non-causal bias, the inter-channel gain parameter, or a combination thereof. A device transmitter may transmit at least one coded signal, the noncausal time mismatch value, the relative gain parameter, the reference channel (or signal) indicator, or a combination thereof. In the present description, terms such as "determination", "calculation", "deviation", "adjustment" etc. can be used to describe how one or more operations are performed. It should be noted that these terms are not to be construed as limiting and other techniques may be used to perform similar operations.

[0045] With reference to FIG. 1, a particular illustrative example of a system is depicted and generally designated 100. System 100 includes a first device 104 communicatively coupled via network 120 to a second device 106. Network 120 may include one or more wireless networks , one or more wired networks, or a combination thereof.

[0046] The first device 104 includes a memory 153, an encoder 134, a transmitter 110 and one or more input interfaces 112. The memory 153 includes a non-transient computer-readable medium that includes the instructions 191. The instructions 191 are executable by encoder 134 to perform one or more of the operations described herein. A first input interface of input interfaces 112 may be coupled to a first microphone 146. A second input interface of input interface 112 may be coupled to a second microphone 148. Encoder 134 may include a width-span encoder Inter-channel Bandwidth (ICBWE) 136. ICBWE encoder 136 may be configured to estimate one or more spectral mapping parameters based on a synthesized non-reference and one non-reference high-band target channel. For example, ICBWE encoder 136 may estimate spectral mapping parameters 188 and obtain mapping parameters 190. Spectral mapping parameters 188 and gain mapping parameters 190 may be referred to as "ICBWE parameters". However, for ease of description, ICBWE parameters may also be referred to as "parameters".

[0047] The second device 106 includes a receiver 160 and a decoder 162. The decoder 162 may include a high-band mid signal decoder 164, a low-band mid signal decoder 166, a high-band residual prediction unit 168 , a low-band residual prediction unit 170, an upmix processor 172, and an ICBWE decoder 174. Decoder 162 may also include one or more other components that are not illustrated in FIG. 1. For example, decoder 162 may include one or more transform units that are configured to transform a time domain channel (e.g., a time domain signal) into a frequency domain (e.g., a signal domain). transformed). Additional details associated with the operations of decoder 162 are described with reference to FIGS. 2 and 3.

[0048] The second device 106 can be coupled to a first speaker 142, a second speaker 144 or both. Although not shown, the second device 106 may include other components such as a processor (e.g., central processing unit), a microphone, a transmitter, an antenna, a memory, and the like.

[0049] During operation, the first device 104 can receive a first audio channel 130 (for example, a first audio signal) through the first input interface of the first microphone 146 and can receive a second audio channel 132 (for example, a example, a second audio signal) through the second input interface of the second microphone 148. The first audio channel 130 can correspond to a right channel or a left channel. The second audio channel 132 can correspond to the other between the right channel or the left channel. A sound source 152 (e.g., a user, a speaker, ambient noise, a musical instrument, etc.) may be closer to the first microphone 146 than the second microphone 148. Therefore, an audio signal from of the sound source 152 can be received at the input interfaces 112 through the first microphone 146 at a time earlier than the time of the second microphone 148. This natural delay in multichannel signal acquisition through the multiple microphones can introduce a temporal misalignment between the first channel audio channel 130 and the second audio channel 132.

[0050] According to an implementation, the first audio channel 130 can be a "reference channel" and the second audio channel 132 can be a "target channel". The target channel can be adjusted (e.g., time shifted) to substantially align with the reference channel. According to another implementation, the second audio channel 132 can be the reference channel and the first audio channel 130 can be the target channel. According to an implementation, the reference channel and the target channel may vary on a frame-by-frame basis. For example, for a first frame, the first audio channel 130 could be the reference channel and the second audio channel 132 could be the target channel. However, for a second frame (e.g., a subsequent frame), first audio channel 130 may be the target channel and second audio channel 132 may be the reference channel. For ease of description, unless otherwise noted below, first audio channel 130 is the reference channel and second audio channel 132 is the target channel. It should be noted that the reference channel described in relation to the audio channels 130, 132 may be independent of a reference channel indicator 192 (e.g., a high-band reference channel indicator). For example, the reference channel indicator 192 may indicate that a highband of any one of channels 130, 132 is the highband reference channel, and the reference channel indicator 192 may indicate a highband reference channel. which can be the same channel or a different channel from the reference channel.

[0051] The encoder 134 can generate a mid signal, a side signal or both, based on the first audio channel 130 and the second audio channel 132 using the techniques described above with respect to Formulas 1 to 4. The encoder 134 can encode the mid signal to generate encoded mid signal 182. Encoder 134 may also generate parameters 184 (e.g., ICBWE parameters, stereo parameters, or both). For example, encoder 134 may generate a residual prediction gain 186 (e.g., a side signal gain) and reference channel indicator 192. Reference channel indicator 192 may indicate, on a frame-by-frame basis, whether the reference channel is the left channel or the right channel. ICBWE encoder 136 can generate spectral mapping parameters 188 and gain mapping parameters 190. Spectral mapping parameters 188 maps the spectrum (or energies) of a high-band non-reference channel to the spectrum of a high-band channel of synthesized non-reference. Gain mapping parameters 190 can map the gain of the non-reference highband channel to the gain of the synthesized non-reference highband channel.

[0052] The transmitter 110 may transmit the bit stream 180, over the network 120, to the second device 106. The bit stream 180 includes at least the encoded mid signal 182 and the parameters 184. According to other implementations, the bit stream 180 can include additional encoded channels (e.g. a side encoded signal) and additional stereo parameters (e.g. inter-channel intensity difference (IID) parameters, inter-channel level difference (ILD) parameters, inter-channel time difference (ITD) parameters, inter-channel phase difference (IPD) parameters, inter-channel sonification parameters, inter-channel pitch parameters, inter-channel gain parameters, etc.).

[0053] The receiver 160 of the second device 106 can receive the bitstream 180 and the decoder 162 decodes the bitstream 180 to generate a first channel (for example, a left channel 126) and a second channel (for example, a right channel 128). The second device 106 can output the left channel 126 through the first speaker 142 and can output the right channel 128 through the second speaker 144. In alternative examples, the left channel 126 and the right channel 128 can be transmitted as one pair of stereo signals to a single speaker output. The operations of decoder 162 are described in more detail with reference to FIGS. 2 to 3.

[0054] With reference to FIG. 2, a particular implementation of the decoder 162 is shown. The decoder 162 includes the high-band mid signal decoder 164, the low-band mid signal decoder 166, the high-band residual prediction unit 168, the high-band residual prediction unit a low-band 170, an up-mix processor 172, an ICBWE decoder 174, a transform unit 202, a transform unit 204, a combiner circuit 206, and a combiner circuit 208.

[0055] The encoded mid signal 182 is provided to the high band mid signal decoder 164 and the low band mid signal decoder 166. The low band mid signal decoder 166 may be configured to decode a low band portion of the encoded mid signal 182 to generate a decoded lowband mid signal 212. As a non-limiting example, if the encoded mid signal 182 is a Super Wideband signal having audio content between 50 Hz and 16 kHz, the lowband portion of the encoded mid signal 182 may span from 50 Hz to 8 kHz and a high band portion of the encoded mid signal 182 may span from 8 kHz to 16 kHz. The lowband mid signal decoder 166 can decode the lowband portion (e.g., the portion between 50 Hz and 8 kHz) of the encoded mid signal 182 to generate the decoded lowband mid signal 212. example above is for illustrative purposes only and should not be construed as limiting. In other examples, the encoded mid signal 182 may be a Wideband signal, a Full-Band signal, etc. The decoded lowband mid signal 212 (e.g., a time domain channel) is provided to the lowband residual prediction unit 170 and a transform unit 204.

[0056] The low-band residual prediction unit 170 may be configured to process the decoded low-band mid signal 212 to generate a low-band residual prediction signal 214 (e.g., a low-band stereo fill channel or a predicted low-band side signal). The "process" may include filtering operations, non-linear processing operations, phase modification operations, resampling operations, or scaling operations. For example, the low-band residual prediction unit 170 may include one or more all-pass decorrelation filters. The low band residual prediction unit 170 can apply the all pass decorrelation filters to the decoded low band mid signal 212 (e.g. in the 16 kHz bandwidth signal) to generate (or "predict") the low band signal. lowband residual prediction 214. Lowband residual prediction signal 214 is provided to transformer unit 202.

[0057] The transform unit 202 may be configured to perform a transform operation on the low-band residual prediction signal 214 to generate a low-band residual prediction signal in the frequency domain 216. It should be noted that prior to the operation of transform, in some implementations, a windowing operation is also performed which is not shown in FIG. 2. The transform unit 202 may perform a Discrete Fourier Transform (DFT) analysis on the low-band residual prediction signal 214 to generate the low-band residual prediction signal in the frequency domain 216. frequency domain low band 216 is provided to up-mix processor 172. Transformer unit 204 may be configured to perform a transform operation on the decoded low band mid signal 212 to generate a frequency domain low band mid signal 218. For example, the transformer unit 204 may perform a DFT analysis on the decoded lowband mid signal 212 to generate the frequency domain lowband mid signal 218. The frequency domain lowband mid signal 218 is provided to processor 172.

[0058] The up-mix processor 172 can be configured to generate a low-band left channel 220 and a low-band right channel 222 based on the low-band residual prediction signal in the frequency domain 216, the mid-band signal frequency domain 218 and one or more parameters 184 received from the first device 104. For example, the up-mix processor 172 may perform an up-mix operation on the low-band mid signal in the frequency domain 218 and the frequency domain residual low-band prediction signal (e.g., a frequency-domain predicted low-band side signal) to generate the low-band left channel 220 and the low-band right channel 222. The stereo parameters 184 may be used during the up-mix operation. For example, the up-mix processor 172 can apply the IID parameters, the ILD parameters, the ITD parameters, the IPD parameters, the inter-channel sonification parameters, the inter-channel pitch parameters and the inter-channel gain parameters during the up-mix operation. Furthermore, the up-mix processor 172 can apply the residual prediction gains 186 to the low-band residual prediction signal in the frequency domain in frequency bands to determine the side signal in the decoder 162. The up-mix processor 172 can use the reference channel indicator 192 to designate the lowband left channel 220 and the lowband right channel 222. For example, the reference channel indicator 192 can indicate whether a lowband reference channel generated by the upstream processor mix 172 corresponds to lowband left channel 220 or lowband right channel 222. Lowband left channel 220 is supplied to blending circuit 206 and lowband right channel 222 is supplied to blending circuit 208. According to some implementations, the up-mix processor 172 includes inverse transform units (not shown) that are configured to perform transform operations on the lowband reference channel and on a lowband target channel to generate channels 220, 222 For example, inverse transform units can apply inverse DFT operations on the lowband reference channels and lowband target channels to generate time domain channels 220, 222.

[0059] The high-band mid signal decoder 164 may be configured to decode the high-band portion of the encoded mid signal 182 to generate a decoded high-band mid signal 224. As a non-limiting example, if the encoded mid signal 182 for a Super Wideband signal with audio content between 50 Hz and 16 kHz, the highband portion of the 182 encoded mid signal can range from 8 kHz to 16 kHz. The high-band MID signal decoder 166 may decode the high-band portion of the encoded MID signal 182 to generate the decoded high-band MID signal 224. The decoded high-band MID signal 224 (e.g., a time-domain channel ) is provided to the high-band residual prediction unit 168 and the ICBWE decoder 174.

[0060] The high-band residual prediction unit 168 may be configured to process the decoded high-band mid signal 224 to generate a high-band residual prediction signal 226 (e.g., a high-band stereo fill channel or a high-band predicted side signal). For example, the high-band residual prediction unit 168 may include one or more all-pass decorrelation filters. The high-band residual prediction unit 168 may apply the all-pass decorrelation filters to the decoded high-band mid signal 224 (e.g., a 16 kHz bandwidth signal) to generate (or "predict") the high-band signal. high-band residual prediction 226. High-band residual prediction signal 226 is provided to ICBWE decoder 174.

[0061] In a particular implementation, the high-band residual prediction unit 168 includes all pass decorrelation filters and a gain mapper. The all-pass decorrelation filters generate a filtered signal (e.g., a time-domain signal) by filtering the decoded high-band mid signal 224. The gain mapper generates the high-band residual prediction signal 226 by performing an operation of gain mapping on the filtered signal.

[0062] In a particular implementation, the high-band residual prediction unit 168 generates the high-band residual prediction signal 226 by performing a spectral mapping operation, a filtering operation, or both. For example, the high-band residual prediction unit 168 generates a spectral mapped signal by performing a spectral mapping operation on the decoded high-band mid signal 224 and generates the high-band residual prediction signal 226 by filtering the mapped signal. spectrally.

[0063] The ICBWE decoder 174 can be configured to generate a high-band left channel 228 and a high-band right channel 230 based on the decoded high-band mid signal 224, the high-band residual prediction signal 226 and the parameters 184 (for example, ICBWE parameters). The operations of ICBWE decoder 174 are described with reference to FIG. 3.

[0064] With reference to FIG. 3, a particular implementation of the ICBWE decoder 174 is shown. The ICBWE decoder 174 includes a high band residual generation unit 302, a spectral mapper 304, a gain mapper 306, a combining circuit 308, a spectral mapper 310, a gain mapper 312, a combination circuit 314 and a channel selector 316.

[0065] The high-band residual prediction signal 226 is provided to the high-band residual generation unit 302. The residual prediction gain 186 (encoded in the bit stream 180) is also provided to the high-band residual generation unit 302. The 302 high-band residual generation unit may be configured to apply the 186 residual prediction gain to the 226 high-band residual predication signal to generate a 324 high-band residual channel (e.g., a high-band side signal ). In some implementations, when there is more than one high-band residual prediction gain on different bands, these gains may be applied differently at different high-band frequencies. This can be accomplished by deriving a filter from the multiple high-band residual prediction gains and filtering the high-band residual prediction signal 226 with that filter to generate the high-band residual channel 324. The high-band residual channel 324 is supplied to combination circuit 314 and spectral mapper 310.

[0066] According to one implementation, for a low-band core of 12.8 kHz, the high-band residual prediction signal 226 (for example, a mid-high-band stereo fill signal) is processed by the generation unit high-band residual 302 using residual predication gains. For example, high band residual generation unit 302 can map two band gains to a first order filter. Processing can be performed in the un-flipped domain (eg covering 6.4 kHz to 14.4 kHz of the 32 kHz signal). Alternatively, processing can be performed on the high-band channel spectrally inverted and down-mixed (eg covering 6.4 kHz to 14.4 kHz in the baseband). For a 16 kHz low-band core, a mid-signal low-band non-linear excitation is mixed with envelope-shaped noise to generate a target high-band non-linear excitation. The target high-band non-linear excitation is filtered using a mid-signal high-band low-pass filter to generate the decoded high-band mid signal 224.

[0067] The decoded high-band mid signal 224 is provided to the combining circuit 314 and the spectral mapper 304. The combining circuit 314 may be configured to combine the decoded high-band mid signal 224 and the high-band residual channel 324 to generate a high-band reference channel 332. In some implementations, prior to generating the high-band reference channel 332, the combined output of the combining circuit 314 may first be scaled with a gain factor based on 190. high-band reference channel 332 is provided to channel selector 316.

[0068] The spectral mapper 304 can be configured to perform a first spectral mapping operation on the decoded high-band mid signal 224 to generate a spectrally mapped high-band mid signal 320. For example, the spectral mapper 304 can apply the spectral mapping parameters 188 (e.g., dequantized spectral mapping parameters) to the decoded high-band mid signal 224 to generate the spectrally mapped high-band mid signal 320. The spectrally mapped high-band mid signal 320 is provided to the gain mapper 306.

[0069] The gain mapper 306 may be configured to perform a first gain mapping operation on the spectrally mapped high band mid signal 320 to generate a first high band gain mapped channel 322. Gain mapping 306 may apply gain mapping parameters 190 to the spectrally mapped high band mid signal 320 to generate the first high band gain mapped channel 322. The first high band gain mapped channel 322 is provided to the gain circuit. combination 308.

[0070] In the implementation illustrated in FIG. 3, ICBWE decoder 174 includes spectral mapper 304. It should be understood that in some other implementations, ICBWE decoder 174 does not include spectral mapper 304. In these implementations, the decoded high-band mid signal 224 is provided to gain mapper 306 (instead of spectral mapper 304) and gain mapper 306 performs the first gain mapping operation on the decoded high band mid signal 224 to generate the first gain band mapped channel 322. For example, gain mapper 306 may apply gain mapping parameters 190 to the decoded highband mid signal 224 to generate the first highband gain mapped channel 322.

[0071] The spectral mapper 310 can be configured to perform a second spectral mapping operation on the high-band residual channel 324 to generate a spectrally mapped high-band residual channel 326. For example, the spectral mapper 310 can apply the parameters from spectral mapping channel 188 to the high-band residual channel 324 to generate the spectrally mapped high-band residual channel 326. The spectrally mapped high-band residual channel 326 is provided to gain mapper 312.

[0072] The gain mapper 312 may be configured to perform a second gain mapping operation on the spectrally mapped high band residual channel 326 to generate a second high band gain mapped channel 328. Gain mapping 312 may apply the gain mapping parameters 190 to the spectrally mapped high band residual channel 326 to generate the second high band gain mapped channel 328. combination 308.

[0073] In the implementation illustrated in FIG. 3, ICBWE decoder 174 includes spectral mapper 310. It should be understood that, in some other implementations, ICBWE decoder 174 does not include spectral mapper 310. In these implementations, high-band residual channel 324 is provided to gain mapper 312 (instead of the spectral mapper 310) and the gain mapper 312 performs the second gain mapping operation on the high band residual channel 324 to generate the second high band gain mapped channel 328. For example, the gain mapper 312 can apply the gain mapping parameters 190 to the high band residual channel 324 to generate the second high band gain mapping channel 328.

[0074] In other alternative implementations, instead of applying spectral mapping on the high-band residual channel 324 and the decoded high-band mid signal 224 independently, combiner 308 can combine channels 324, 224, spectral mapper 304 can perform a spectral mapping operation on the combined channels, and the gain mapper 306 may perform gain mapping on the resulting channel to generate the high-band target channel 330. In another alternative implementation, the spectral mapping operations on the high-band residual channel 324 and the decoded high-band mid signal 224 can be performed independently, combiner 308 can combine the resulting channels, and gain mapper 306 can apply a gain to generate the target high-band channel 330.

[0075] The combination circuit 308 may be configured to combine the first high-band gain-mapped channel 322 and the second high-band gain-mapped channel 328 to generate a high-band target channel 330. The high-band target channel 330 is provided to channel selector 316.

[0076] Channel selector 316 may be configured to designate one of the high-band reference channel 332 or high-band target channel 330 as the high-band left channel 228. Channel selector 316 may also be configured to designate the other one of the 332 high-band reference channel or the 330 high-band target channel as the 230 high-band right channel. For example, the 192 reference channel flag is provided to the 316 channel selector. channel selector 192 has a binary value of "0", the channel selector 316 designates the high-band reference channel 332 as the left high-band channel 228 and designates the high-band target channel 330 as the right channel of highband 230. If the reference channel indicator 192 has a binary value of "1", the channel selector 316 designates the highband reference channel 332 as the highband right channel 230 and designates the highband target channel high 330 as the high band left channel 228.

[0077] Returning to FIG. 2, the high-band left channel 228 is supplied to the combination circuit 206 and the high-band right channel 230 is supplied to the combination circuit 208. The combination circuit 206 may be configured to combine the low-band left channel 220 and the highband left channel 228 to generate the left channel 126 and the combining circuit 208 can be configured to combine the lowband right channel 222 and the highband right channel 230 to generate the right channel 128.

[0078] The techniques described with respect to FIGS. 1 to 3 can reduce computational complexity by ignoring the resampling operations of the decoded lowband mid signal 212. For example, instead of resampling the decoded lowband mid signal 212 at 32 kHz, combine the resampled signal with the mid signal of decoded highband signal 224 and determine a residual prediction signal (e.g., a stereo fill channel or side signal) based on the combined signal, the residual prediction of the decoded lowband mid signal 212 can be separately determined. As a result, the computational complexity associated with resampling the decoded low-band mid signal 212 is reduced, and DFT analysis of the low-band residual prediction signal 214 can be performed at 16 kHz (as opposed to 32 kHz).

[0079] With reference to FIG. 4, a method 400 of processing an encoded bit stream is shown. Method 400 may be performed by the second device 106 of FIG. 1. More specifically, method 400 can be performed by receiver 160 and decoder 162.

[0080] Method 400 includes receiving, at a decoder, a bit stream that includes an encoder mid signal, at 402. For example, referring to FIG. 1, receiver 160 may receive bit stream 180 from first device 104. Bit stream 180 includes encoded mid signal 182 and parameters 184.

[0081] Method 400 also includes decoding a lowband portion of the encoded mid signal to generate a decoded lowband mid signal, at 404. For example, referring to FIG. 2, the lowband mid signal decoder may decode the lowband portion of the encoded mid signal 182 to generate the decoded lowband mid signal 212. Method 400 also includes processing the decoded lowband mid signal to generate a signal. low-band residual prediction at 406. For example, referring to FIG. 2, the lowband residual prediction unit 170 can process the decoded lowband mid signal 212 to generate the lowband residual prediction signal 214.

[0082] The method 400 also includes generating a lowband left channel and a lowband right channel based partially on the decoded lowband mid signal and the lowband residual prediction signal at 408. For example, referring to if to FIG. 2, the transform unit 202 can perform a first transform operation on the lowband residual prediction signal 214 to generate the lowband residual prediction signal in the frequency domain 216. The transform unit 204 can perform a second transform operation. transformed into the decoded low-band mid signal 212 to generate the low-band mid signal 218 in the frequency domain. Up-mix processor 172 may receive parameters 184 (including reference channel indicator 192 and residual prediction gain 186) and up-mix processor 172 may perform an up-mix operation to generate the low-band left channel 220 and the lowband right channel 222 based on the parameters 184, the frequency domain lowband mid signal 218, and the frequency domain lowband residual prediction signal 216.

[0083] Method 400 also includes decoding a highband portion of the encoded mid signal to generate a decoded highband mid signal, at 410. For example, referring to FIG. 2, high-band mid signal decoder 164 can decode the high-band portion of encoded mid signal 182 to generate decoded high-band mid signal 224. Method 400 also includes processing the decoded high-band mid signal to generate a high-band residual prediction signal, at 412. For example, referring to FIG. 2, the high-band residual prediction unit 168 can process the decoded high-band mid signal 224 to generate the high-band residual prediction signal 226. In another implementation, the high-band residual prediction signal 226 can be estimated to from the low-band residual prediction signal 214. For example, the high-band residual prediction signal 226 can be estimated based on a non-linear harmonic bandwidth extension of the low-band residual prediction signal 214. In an alternative implementation, the high-band residual prediction signal 226 may be based on temporally and spectrally modeled noise. The temporally and spectrally modeled noise can be based on lowband parameters and highband parameters.

[0084] The method 400 also includes generating a high-band left channel and a high-band right channel based on the decoded high-band mid signal and the high-band residual prediction signal at 414. For example, referring to to FIGS. 2-3, the ICBWE decoder 174 can generate the high-band left channel 228 and the high-band right channel 230 based on the decoded high-band mid signal 224 and the high-band residual prediction signal 226. To illustrate, the high-band residual generation unit 302 applies the residual prediction gain 186 to the high-band residual prediction signal 226 to generate the high-band residual channel 324. The combination circuit 314 combines the decoded high-band mid signal 224 and the high-band residual channel 324 to generate high-band reference channel 332.

[0085] Additionally, the spectral mapper 304 performs the first spectral mapping operation on the decoded high-band mid signal 224 to generate the spectrally mapped high-band mid signal 320. The gain mapper 306 performs the first mapping operation by gain on the spectrally mapped high band mid signal 320 to generate the first high band gain mapped channel 322. The spectral mapper 310 performs the second spectral mapping operation on the high band residual channel 324 to generate the band residual channel The 326 spectrally mapped high band residual channel 326. The 312 gain mapper performs the second gain mapping operation on the 326 spectrally mapped high band residual channel to generate the 328 second high band gain mapping channel. The high-band gain mapping channel 322 and the second high-band gain mapping channel 328 are combined to generate the high-band target channel 330. Based on the reference channel indicator 192, one of the channels 330, 332 is designated as high-band left channel 228 and the other between channels 330, 332 is designated as high-band right channel 230.

[0086] The method 400 also includes outputting a left channel and a right channel at 416. The left channel can be based on the low band left channel and the high band left channel, and the right channel can be based on on the low-band right channel and the high-band right channel. For example, referring to FIG. 2, the combining circuit 206 can combine the left lowband channel 220 and the left highband channel 228 to generate the left channel 126, and the combining circuit 208 can combine the right lowband channel 222 and the right channel highband 230 to generate right channel 128. Speakers 142, 144 of FIG. 1 can output channels 126, 128 respectively.

[0087] Method 400 of FIG. 4 can reduce computational complexity by skipping or omitting resampling operations on the decoded low-band mid signal 212. For example, instead of resampling the decoded low-band mid signal 212 at 32 kHz, combine the resampled signal with the high-band mid signal decoded high band 224 and determine a residual prediction signal (e.g., a stereo fill channel or side signal) based on the combined signal, the residual prediction of the decoded low band mid signal 212 may be separately determined. As a result, the computational complexity associated with resampling the decoded low-band mid signal 212 is reduced, and DFT analysis of the low-band residual prediction signal 214 can be performed at 16 kHz (as opposed to 32 kHz).

[0088] With reference to FIG. 5, a block diagram of a particular illustrative example of a device (eg, a wireless communication device) and generally designated 500 is depicted. In various implementations, device 500 may have fewer or more components than illustrated in FIG. . 5. In an illustrative implementation, device 500 may correspond to first device 104 of FIG. 1 or the second device 106 of FIG. 1. In an illustrative implementation, device 500 can perform one or more operations described with reference to systems and methods of FIGS. 1 to 4.

[0089] In a particular implementation, the device 500 includes a processor 506 (eg, a central processing unit (CPU)). Device 500 may include one or more processors 510 (e.g., one or more digital signal processors (DSPs)). Processors 510 may include a media (eg, speech and music) encoder/decoder (CODEC) 508 and an echo canceller 512. Media CODEC 508 may include decoder 162, encoder 134, or a combination thereof.

[0090] Device 500 may include a memory 553 and a CODEC 534. Although media CODEC 508 is illustrated as a component of processors 510 (e.g., dedicated circuitry and/or executable programming code), in other implementations one or more components of media CODEC 508, such as decoder 162, encoder 134, or a combination thereof, may be included in processor 506, CODEC 534, another processing component, or a combination thereof.

[0091] The device 500 may include the receiver 160 coupled to an antenna 542. The device 500 may include a screen 528 coupled to a display controller 526. One or more speakers 548 may be coupled to the CODEC 534. One or more microphones 546 may be coupled, via input interface(s) 112, to CODEC 534. In a particular implementation, speakers 548 may include first speaker 142, second speaker 144 of FIG. 1, or a combination thereof. In a particular implementation, microphones 546 may include first microphone 146, second microphone 148 of FIG. 1, or a combination thereof. CODEC 534 may include a digital to analog converter (DAC) 502 and an analog to digital converter (ADC) 504.

[0092] The memory 553 may include instructions 591 executable by the processor 506, by the processors 510, by the CODEC 534, by another processing unit of the device 500, or by a combination thereof, to perform one or more operations described with reference to FIGS. . 1 to 4.

[0093] One or more components of device 500 may be implemented through dedicated hardware (eg, circuitry), by a processor executing instructions to perform one or more tasks, or a combination thereof. As an example, memory 553 or one or more components of processor 506, processors 510 and/or CODEC 534 may be a memory device such as random access memory (RAM), magnetoresistive random access memory (MRAM ), Rotational Torque Transfer MRAM (STT-MRAM), Flash Memory, Read-Only Memory (ROM), Programmable Read-Only Memory (PROM), Programmable Read-Only Erasable Memory (EPROM), Memory Only electrically erasable programmable read-only memory (EEPROM), registers, hard disk, a removable disk, or read-only memory on a compact disk (CD-ROM). The memory device may include instructions (for example, the 591 instructions) that, when executed by a computer (for example, a processor on the 534 CODEC, the 506 processor, and/or the 510 processors), can cause the computer to execute one or more operations described with reference to FIGS. 1 to 4. As an example, memory 553 or the one or more components of processor 506, processors 510 and/or CODEC 534 may be a non-transient computer-readable medium that includes instructions (e.g., instructions 591) which, when executed by a computer (e.g., a processor at CODEC 534, processor 506, and/or processors 510), causes the computer to perform one or more operations described with reference to FIGS. 1 to 4.

[0094] In a particular implementation, the device 500 may be included in a system-on-a-package or system-on-a-chip device (e.g., a mobile station modem (MSM)) 522. In a particular implementation, the processor 506, the processors 510, display controller 526, memory 553, CODEC 534, and receiver 160 are included in a system-on-package or system-on-chip device 522. In a particular implementation, an input device 530, such as a touch screen and/or keypad, and a power supply 544 are coupled to system-on-chip device 522. Furthermore, in one particular implementation, as illustrated in FIG. 5, screen 528, input device 530, speakers 548, microphones 546, antenna 542, and power supply 544 are external to system-on-chip device 522. However, each of the screens 528, the Input devices 530, speakers 548, microphones 546, antenna 542 and power supply 544 may be coupled to a system-on-chip device component 522, such as an interface or a controller.

[0095] The device 500 may include a cordless phone, a mobile communication device, a mobile phone, a smart phone, a cell phone, a laptop computer, a desktop computer, a computer, a tablet, a set top box , a personal digital assistant (PDA), a display device, a television, a game console, a music player, a radio, a video player, an entertainment unit, a communication device, a data drive fixed location, a personal media player, a digital video player, a digital video disc (DVD) player, a tuner, a camera, a navigation device, a decoder system, an encoder system, or any combination thereof.

[0096] With reference to FIG. 6, a block diagram of a particular illustrative example of a base station 600 is depicted. In various implementations, base station 600 may have more components or fewer components than illustrated in FIG. 6. In an illustrative example, base station 600 may include first device 104 or second device 106 of FIG. 1. In an illustrative example, base station 600 can operate in accordance with one or more of the methods or systems described with reference to FIGS. 1 to 4.

[0097] The base station 600 may be part of a wireless communication system. The wireless communication system can include multiple base stations and multiple wireless devices. The wireless communication system may be a Long Term Evolution (LTE) system, a Code Division Multiple Access (CDMA) system, a Global System for Mobile Communications (GSM), a wireless LAN system ( WLAN) or some other wireless system. A CDMA system may implement Wideband CDMA (WCDMA), CDMA 1X, Optimized Data Evolution (EVDO), Time Division Synchronous CDMA (TD-SCDMA), or some other version of CDMA.

[0098] Wireless devices can also be referred to as user equipment (UE), a mobile station, a terminal, an access terminal, a subscriber unit, a station, etc. Wireless devices can include a cell phone, a smart phone, a tablet, a wireless modem, a personal digital assistant (PDA), a handheld device, a laptop, a smartbook, a netbook, a tablet, a cordless phone , a wireless local loop station (WLL), a Bluetooth device, etc. Wireless devices can include or correspond to device 600 of FIG. 6.

[0099] Various functions may be performed by one or more base station components 600 (and/or other components not shown), such as sending and receiving messages and data (eg, audio data). In a particular example, base station 600 includes a processor 606 (e.g., a CPU). Base station 600 may include a transcoder 610. Transcoder 610 may include an audio CODEC 608. For example, transcoder 610 may include one or more components (e.g., circuitry) configured to perform the operations of the audio CODEC 608. As another example, transcoder 610 can be configured to carry out one or more computer-readable instructions to perform the operations of audio CODEC 608. Although audio CODEC 608 is illustrated as a component of transcoder 610, in other examples a or more audio CODEC components 608 may be included in processor 606, another processing component, or a combination thereof. For example, a decoder 638 (e.g., a vocoder decoder) can be included in a receiver data processor 664. As another example, an encoder 636 (e.g., a vocoder encoder) can be included in a receiver data processor. broadcast data 682.

[0100] The transcoder 610 can function to transcode messages and data between two or more networks. Transcoder 610 may be configured to convert message and audio data from a first format (e.g., a digital format) to a second format. To illustrate, decoder 638 can decode encoded signals having a first format, and encoder 636 can encode the decoded signals into encoded signals having a second format. Additionally or alternatively, transcoder 610 may be configured to perform data rate adaptation. For example, transcoder 610 can down convert a data rate or up convert a data rate without changing a format of the audio data. To illustrate, transcoder 610 can downconvert 64 kbit/s signals to 16 kbit/s signals.

[0101] Audio CODEC 608 may include encoder 636 and decoder 638. Encoder 636 may include encoder 134 of FIG. 1. Decoder 638 may include decoder 162 of FIG. 1.

[0102] Base station 600 may include memory 632. Memory 632, such as a computer-readable storage device, may include instructions. Instructions may include one or more instructions executable by processor 606, transcoder 610, or a combination thereof, to perform one or more operations described with reference to the methods and systems of FIGS. 1 to 4. Base station 600 may include multiple transmitters and receivers (e.g., transceivers), such as a first transceiver 652 and a second transceiver 654, coupled to an array of antennas. The antenna array can include a first antenna 642 and a second antenna 644. The antenna array can be configured to communicate wirelessly with one or more wireless devices, such as device 600 of FIG. 6. For example, the second antenna 644 may receive a stream of data 614 (eg, a stream of bits) from a wireless device. Data stream 614 can include messages, data (e.g., encoded speech data), or a combination thereof.

[0103] The base station 600 may include a network connection 660, such as a backhaul connection. Network connection 660 can be configured to communicate with a core network or with one or more base stations of the wireless communication network. For example, base station 600 may receive a second stream of data (e.g., messages or audio data) from a core network over network connection 660. Base station 600 may process the second stream of data to generate audio messages or data and deliver the messages or audio data to one or more wireless devices through one or more antennas of the antenna array or to another base station through network connection 660. In a particular implementation, the connection network connection 660 may be a wide area network (WAN) connection, as an illustrative and non-limiting example. In some implementations, the core network may include or correspond to a public switched telephone network (PSTN), a bundled core (backbone) network, or both.

[0104] The base station 600 may include a media gateway 670 that is coupled to the network connection 660 and the processor 606. The media gateway 670 may be configured to convert between media streams of different telecommunications technologies. For example, Media Gateway 670 can convert between different transmission protocols, between different encoding schemes, or between both. To illustrate, media gateway 670 can convert from PCM signals to Real Time Transport Protocol (RTP) signals, as an illustrative and non-limiting example. The 670 media gateway can convert data between packet-switched networks (e.g., a Voice Over Internet Protocol (VoIP) network, an IP Multimedia System (IMS), a fourth generation (4G) wireless network, such as LTE , WiMax and UMB, etc., circuit-switched networks (for example, a PSTN) and hybrid networks (for example, a second generation (2G) wireless network such as GSM, GPRS and EDGE, a third generation (3G), such as WCDMA, EV-DO and HSPA, etc.).

[0105] Additionally, media gateway 670 can include transcoding and can be configured to transcode data when codecs are incompatible. For example, the 670 media gateway can transcode between an Adaptive Multi-Rate (AMR) codec and a G.711 codec, as an illustrative and non-limiting example. Media gateway 670 may include a router and a plurality of physical interfaces. In some implementations, the 670 media gateway may also include a controller (not shown). In a particular implementation, the media gateway controller can be external to media gateway 670, external to base station 600, or external to both. The Media Gateway Controller can control and coordinate the operations of multiple Media Gateways. The 670 media gateway can receive control signals from the media gateway controller and can function to bridge different transmission technologies and can add service to end-user resources and connections.

[0106] The base station 600 may include a demodulator 662 that is coupled to the transceivers 652, 654, the receiver data processor 664 and the processor 606, and the receiver data processor 664 may be coupled to the processor 606. The demodulator 662 may be configured to demodulate modulated signals received from transceivers 652, 654 and to provide demodulated data to receiver data processor 664. Receiver data processor 664 may be configured to extract message or audio data from the demodulated data and send the message or audio data to processor 606.

[0107] The base station 600 may include a transmission data processor 682 and a multiple-input, multiple-output (MIMO) transmission processor 684. The transmission data processor 682 may be coupled with the processor 606 and the MIMO processor of transmission 684. Transmission MIMO processor 684 may be coupled to transceivers 652, 654 and processor 606. In some implementations, transmission MIMO processor 684 may be coupled to media gateway 670. Transmission data processor 682 may be coupled to configured to receive messages or audio data from processor 606 and encode the messages or audio data based on an encoding scheme, such as CDMA or orthogonal frequency division multiplexing (OFDM), as an illustrative example and not limiting. Stream data processor 682 may provide the encoded data to stream MIMO processor 684.

[0108] Encoded data can be multiplexed with other data, such as pilot data, using CDMA or OFDM techniques to generate multiplexed data. The multiplexed data may then be modulated (i.e., symbol mapped) by transmit data processor 682 based on a particular modulation scheme (e.g., Binary Phase Shift Keying ("BPSK"), Binary Phase Shift Keying ("BPSK") Quadrature Phase ("QSPK"), M-ary Phase Shift Modulation ("M-PSK"), M-ary Quadrature Amplitude Modulation ("M-QAM"), etc.) to generate modulation symbols . In a particular implementation, the coded data and the other data may be modulated using different modulation schemes. The data, encoding, and modulation rate for each data stream can be determined by instructions executed by processor 606.

[0109] The transmit MIMO processor 684 can be configured to receive the modulation symbols from the transmit data processor 682 and can further process the modulation symbols and can perform beamshaping on the data. For example, transmit MIMO processor 684 can apply beamforming weights to modulation symbols. The beamshaping weights may correspond to one or more antennas of the antenna array from which the modulation symbols are transmitted.

[0110] During operation, the second antenna 644 of the base station 600 can receive a data stream 614. The second transceiver 654 can receive the data stream 614 from the second antenna 644 and can deliver the data stream 614 to the demodulator 662. Demodulator 662 can demodulate modulated signals from data stream 614 and provide demodulated data to receiver data processor 664. Receiver data processor 664 can extract audio data from the demodulated data and provide the audio data extracted for the 606 processor.

[0111] Processor 606 may provide the audio data to transcoder 610 for transcoding. Decoder 638 of transcoder 610 can decode the audio data from a first format into decoded audio data, and encoder 636 can encode the decoded audio data into a second format. In some implementations, encoder 636 may encode the audio data using a higher data rate (e.g., upconversion) or a lower data rate (e.g., downconversion) than that received at from the wireless device. In other implementations, audio data may not be transcoded. While transcoding (eg, decoding and encoding) is illustrated as being performed by one transcoder 610, transcoding operations (eg, decoding and encoding) may be performed by multiple components of base station 600. For example, decoding may be performed by receiver data processor 664 and encoding may be performed by transmit data processor 682. In other implementations, processor 606 may provide the audio data to media gateway 670 for conversion to another transmission protocol, to another encoding scheme or to both. Media gateway 670 may deliver the converted data to another base station or core network via network connection 660.

[0112] Encoded audio data generated in the encoder 636, such as transcoded data, can be provided to the transmission data processor 682 or for network connection 660 through the processor 606. The transcoded audio data from the transcoder 610 can be provided to transmission data processor 682 for encoding according to a modulation scheme, such as OFDM, to generate the modulation symbols. Stream data processor 682 may provide the modulation symbols to stream MIMO processor 684 for further processing and beam shaping. The transmit MIMO processor 684 can apply beamshaping weights and can provide the modulation symbols to one or more antennas of the antenna array, such as the first antenna 642 through the first transceiver 652. Thus, the base station 600 can provide a transcoded data stream 616 corresponding to the data stream 614 received from the wireless device to another wireless device. Transcoded data stream 616 may have a different encoding format, data rate, or both than data stream 614. In other implementations, transcoded data stream 616 may be provided to network connection 660 for transmission to another base station or to a core network.

[0113] In a particular implementation, one or more components of the systems and devices described in this document may be integrated within a system or decoding apparatus (for example, an electronic device, a CODEC or a processor within it), within a encoding system or apparatus, or both. In other implementations, one or more of the systems and devices described in this document may be integrated into a cordless phone, a tablet computer, a desktop computer, a laptop computer, a set top box, a music player, a video player, entertainment unit, television, game console, navigation device, communication device, personal digital assistant (PDA), fixed location data unit, personal media player, or other device type.

[0114] In conjunction with the described techniques, an apparatus includes means for receiving an encoded mid signal. For example, the means for receiving the encoded MID signal may include the receiver 160 of FIGS. 1 and 5, the decoder 162 of FIGS. 1, 2, and 5, decoder 638 of FIG. 6, one or more other devices, circuits, modules or any combination thereof.

[0115] The apparatus also includes means for decoding a lowband portion of the encoded mid signal to generate a lowband decoded mid signal. For example, the means for decoding may include decoder 162 of FIGS. 1, 2, and 5, the low-band mid signal decoder 166 of FIGS. 1 to 2, the CODEC 508 of FIG. 5, processor 506 of FIG. 5, instructions 591 executable by a processor, decoder 638 of FIG. 6, one or more other devices, circuits, modules or any combination thereof.

[0116] The apparatus also includes means for processing the decoded lowband mid signal to generate a lowband residual prediction signal. For example, the means for processing may include the decoder 162 of FIGS. 1, 2, and 5, the low-band residual prediction unit 170 of FIGS. 1 to 2, the CODEC 508 of FIG. 5, processor 506 of FIG. 5, instructions 591 executable by a processor, decoder 638 of FIG. 6, one or more other devices, circuits, modules or any combination thereof.

[0117] The apparatus also includes means for generating a lowband left channel and a lowband right channel based partially on the decoded lowband mid signal and the lowband residual prediction signal. For example, the means for generating may include decoder 162 of FIGS. 1, 2 and 5, the up-mix processor 172 of FIGS. 1-2, the CODEC 508 of FIG. 5, processor 506 of FIG. 5, instructions 591 executable by a processor, decoder 638 of FIG. 6, one or more other devices, circuits, modules or any combination thereof.

[0118] The apparatus also includes means for decoding a high band portion of the encoded mid signal to generate a decoded high band mid signal. For example, the means for decoding may include decoder 162 of FIGS. 1, 2, and 5, the high-band mid signal decoder 164 of FIGS. 1-2, the CODEC 508 of FIG. 5, processor 506 of FIG. 5, instructions 591 executable by a processor, decoder 638 of FIG. 6, one or more other devices, circuits, modules or any combination thereof.

[0119] The apparatus also includes means for processing the decoded high-band mid signal to generate a high-band residual prediction signal. For example, the means for processing may include the decoder 162 of FIGS. 1, 2, and 5, the high-band residual prediction unit 168 of FIGS. 1 to 2, the CODEC 508 of FIG. 5, processor 506 of FIG. 5, instructions 591 executable by a processor, decoder 638 of FIG. 6, one or more other devices, circuits, modules or any combination thereof.

[0120] The apparatus also includes means for generating a high-band left channel and a high-band right channel based on the decoded high-band mid signal and the high-band residual prediction signal. For example, the means for generating may include decoder 162 of FIGS. 1, 2, and 5, the ICBWE decoder 174 of FIGS. 1-3, the high-band residual generation unit 302 of FIG. 3, the spectral mapper 304 of FIG. 3, the spectral mapper 310 of FIG. 3, the gain mapper 306 of FIG. 3, gain mapper 312 of FIG. 3, combination circuits 308, 314 of FIG. 3, channel selector 316 of FIG. 3, the CODEC 508 of FIG. 5, processor 506 of FIG. 5, instructions 591 executable by a processor, decoder 638 of FIG. 6, one or more other devices, circuits, modules or any combination thereof.

[0121] The apparatus also includes means for outputting a left channel and a right channel. The left channel can be based on the lowband left channel and the highband left channel, and the right channel can be based on the lowband right channel and the highband right channel. For example, means for broadcasting could include loudspeakers 142, 144 of FIG. 1, speakers 548 of FIG. 5, one or more other devices, circuits, modules or any combination thereof.

[0122] It should be noted that several functions performed by one or more components of the systems and devices described in this document are described as being performed by certain components or modules. This division of components and modules is merely illustrative. In an alternative implementation, a function performed by a particular component or module may be split across multiple components or modules. Furthermore, in an alternative implementation, two or more components or modules may be integrated within a single component or module. Each component or module can be implemented using hardware (for example, a field-programmable gate array device (FPGA), application-specific integrated circuit (ASIC), DSP, controller, etc.), software (for example, instructions executable by a processor) or any combination thereof.

[0123] Those skilled in the art should further understand that the various logic blocks, configurations, modules, circuits, and illustrative algorithm steps described in connection with the implementations described in this document may be implemented as electronic hardware, computer software executed by a device of processing, such as a hardware processor, or combinations of both. Various illustrative components, blocks, configurations, modules, circuits, and steps have been described above generally in terms of their functionality. Whether this functionality is implemented as hardware or executable software depends on the particular application and design constraints imposed on the overall system. Skilled technicians may implement the described functionality in various ways for each particular application, but such implementation decisions should not be construed as causing a departure from the scope of the present description.

[0124] The steps of a method or an algorithm described in connection with the implementations described in this document can be incorporated directly in hardware, in a software module executed by a processor or in a combination of the two. A software module may reside in a memory device such as random access memory (RAM), magnetoresistive random access memory (MRAM), torque transfer MRAM (STT-MRAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disk, a removable disk, or memory read-only on compact disc (CD-ROM). An exemplary memory device is coupled to the processor so that the processor can read information from and write information to the memory device. Alternatively, the memory device may be an integral part of the processor. The processor and storage medium may reside on an Application Specific Integrated Circuit (ASIC). The ASIC can reside on a computing device or on a user terminal. Alternatively, the processor and storage medium may reside as discrete components in a computing device or user terminal.

[0125] The previous description of the described implementations is provided to allow a person skilled in the art to make or use the described implementations. Various modifications to these implementations will be readily apparent to those skilled in the art, and the principles defined in this document can be applied to other implementations without departing from the scope of the description. Thus, the present description is not intended to be limited to the implementations shown in this document, but should be given the widest possible scope, consistent with the principles and new features, as defined by the following claims.

Claims (15)

1. Device, comprising: a lowband mid signal decoder configured to decode a lowband portion of an encoded mid signal to generate a decoded lowband mid signal, wherein the encoded mid signal corresponds to a sum of a first audio signal and a second audio signal; a lowband residual prediction unit configured to process the decoded lowband mid signal to generate a lowband residual prediction signal; an up-mix processor configured to generate a lowband left channel and a lowband right channel based partially on the decoded lowband mid signal and the lowband residual prediction signal; a high band mid signal decoder configured to decode a high band portion of the encoded mid signal to generate a time domain decoded high band mid signal; a high-band residual prediction unit configured to process the time-domain decoded high-band mid signal to generate a high-band time-domain residual prediction signal; and an inter-channel bandwidth extension decoder configured to generate a high-band left channel and a high-band right channel based on the time-domain decoded high-band mid signal and the high-band residual prediction signal in the time domain. 2. Device according to claim 1, characterized in that it comprises a receiver configured to receive a bit stream that includes the encoded mid signal, one or more parameters and a reference channel indicator, the one or more parameters comprising a residual prediction gain, wherein the up-mix processor is further configured to generate the lowband left channel and the lowband right channel at least partially based on the one or more parameters and the reference channel flag. 3. Device according to claim 1, characterized in that the high-band residual prediction unit comprises: one or more pass filters all configured to generate a time-domain filtered signal by filtering the high-band mid signal decoded in the time domain; and a gain mapper configured to generate the high-band residual prediction signal in the time domain by performing a gain mapping operation on the filtered time domain signal. 4. Device according to claim 1, characterized in that the high-band residual prediction unit is further configured to: generate a spectral mapped signal by performing a spectral mapping operation on the decoded high-band mid signal in the time domain; and generating the high-band residual prediction signal in the time domain by filtering the spectral mapped signal. 5. Device according to claim 1, characterized in that it additionally comprises: a first combination circuit configured to combine the low-band left channel and the high-band left channel to generate a left channel; a second combining circuit configured to combine the lowband right channel and the highband right channel to generate a right channel; and an output device configured to output the left channel and the right channel. 6. Device according to claim 1, characterized in that the inter-channel bandwidth extension decoder comprises: a high-band residual generation unit configured to apply a residual prediction gain to the residual prediction signal high-band time domain to generate a high-band residual channel; and a third combining circuit configured to combine the time-domain decoded high-band mid signal and the high-band residual channel to generate a high-band reference channel. 7. Device according to claim 6, characterized in that the inter-channel bandwidth extension decoder further comprises: a first spectral mapper configured to perform a first spectral mapping operation on the decoded high-band mid signal in the time domain to generate a spectral mapped high-band mid signal; and a second spectral mapper configured to perform a second spectral mapping operation on the highband residual channel to generate a spectrally mapped highband residual channel. 8. Device according to claim 6, characterized in that the inter-channel bandwidth extension decoder further comprises a first gain mapper configured to perform a first gain mapping operation on the high-band mid signal decoded in the time domain to generate a high-bandwidth gain-mapped first channel. 9. Device according to claim 8, characterized in that the inter-channel bandwidth extension decoder further comprises a second gain mapper configured to perform a second gain mapping operation on the high-band residual channel to generate a second high-bandgain mapped channel. 10. Device according to claim 9, characterized in that the inter-channel bandwidth extension decoder further comprises: a fourth combining circuit configured to combine the first high-bandwidth mapped channel and the second high-band gain mapped channel to generate a high-band target channel; and a channel selector configured to: receive a reference channel indicator; and based on the flag of the reference channel: designate one of the high-band reference channel or high-band target channel as the high-band left channel; and designating the other one of the highband reference channel or the highband target channel as the highband right channel. 11. Device according to claim 1, characterized in that the low-band mid signal decoder, the low-band residual prediction unit, the up-mix processor, the high-band mid signal decoder, the high-band residual prediction unit and inter-channel bandwidth extension decoder are integrated within a base station. 12. Device according to claim 1, characterized in that the low-band mid signal decoder, the low-band residual prediction unit, the up-mix processor, the high-band mid signal decoder, the high-band residual prediction unit, and inter-channel bandwidth extension decoder are integrated within a mobile device. 13. Method characterized in that it comprises: decoding a lowband portion of an encoded mid signal to generate a decoded lowband mid signal, wherein the encoded mid signal corresponds to a sum of a first audio signal and a second audio signal; processing the decoded lowband mid signal to generate a lowband residual prediction signal; generating a lowband left channel and a lowband right channel based partially on the decoded lowband mid signal and the lowband residual prediction signal; decoding a highband portion of the encoded mid signal to generate a decoded highband mid signal; processing the decoded high-band mid signal to generate a high-band residual prediction signal; and generating a highband left channel and a highband right channel based on the decoded highband mid signal and the highband residual prediction signal. 14. The method of claim 13, further comprising: performing a first transform operation on the low-band residual prediction signal to generate a low-band residual prediction signal in the frequency domain; and performing a second transform operation on the decoded lowband mid signal to generate a frequency domain lowband mid signal. 15. Computer-readable memory characterized by the fact that it comprises instructions stored therein, the instructions being executable by a computer to carry out the method steps as defined in any one of claims 13 to 14.